On Alphamom, Lindsey "Filth Wizardry" Boardman shows how she and her kids made cookie-stamps out of salt-dough (they also make them out of polymer clay, but this is not recommended for use with things you plan on eating). The stamps let each kid customize her cookies, which resolves ownership squabbles and also adds aesthetic appeal.
I made them some handles from the salt dough that we could glue on once they were baked solid. The trick with salt dough is to bake it long and slow so that it doesn't have any problems with air pockets distorting it. We left ours to air dry overnight and then I popped them in the oven on a low heat to finish them the next day.
Happily we found that the salt dough stamps worked nearly as well as the polymer clay one had! Although they are unlikely to last as long or be as easy to clean.